In the medical industry, there is often a need for a laboratory technician, e.g., a cytotechnologist, to review a cytological specimen for the presence of specified cell types. For example, there is presently a need to review a cervical-vaginal Papanicolaou (Pap) smear slides. Pap smears have been a powerful tool for detecting cancerous and precancerous cervical lesions.
The Pap smear has been credited with reducing mortality from cervical cancer by as much as 70%. This once precipitous drop in the death rate has slowed however, and the mortality rate in the United States for this preventable disease has remained virtually constant, at about 5,000 per year since the mid-eighties. Therefore, about one-third of the 15,000 women diagnosed with cervical cancer annually still die, because the cancer was detected too late.
The prevalence of high grade cervical disease has been decreasing where effective screening programs have been implemented. The prevalence is expected to decrease even further with the adoption of new HPV vaccines. With this decrease in prevalence, there has been an increase in the difficulty of maintaining, monitoring, and measuring cytotechnologist diligence during cytological slide examinations. For example, accurately measuring the sensitivity of an individual screener is difficult when the number of abnormal cases is very low. Also, research of visual search tasks has shown that examiner vigilance and alertness decrease with low target prevalence (e.g., low numbers of abnormal cases).
One technique that has been used to counter quality control difficulties caused by low prevalence of abnormal cases is the seeding of known abnormal slides into the rapid screening workflow of reviewers examining Pap smear slides. Though this technique was implemented in a high volume clinical lab over an extended period of time, the technique required a tedious process of selecting abnormal slides, disguising seeded slides to avoid their identification as seeded slides, and excessive slide handling. A more practical and simpler method for seeding abnormal cases into the workflow of cytological examination is needed.